Unfortunately, the Simpsons started getting stale when Homer went from being a mean (albeit hilarious) character to a predictably dumb one. I always wondered why Groening let the show take more of a mainstream feel, rather than letting its "raw" quality envelop the show.

If you get the chance, just listen to the difference in Homer and Marge's voice-overs from the first season to the more recent (last 5 years) episodes. You'll never believe they came from the same voice actors.